Reptile | Article about reptile by The Free Dictionary Reptile | Article about reptile by The Free Dictionary reptile, name for the dry-skinned, usually scaly, cold-blooded vertebrates (see Chordata Chordata , phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals. ..... Click the link for more information. ) of the order Reptilia. Reptiles are found in a variety of habitats throughout the warm and temperate regions (except on some islands), with the greatest variety in the tropics. Reptiles differ from other terrestrial vertebrates (birds and mammals) in that they are cold-blooded, that is, they lack an effective system for regulating their body temperature, which tends to approach that of the environment. For this reason reptiles are not found in the coldest regions of the world, and they hibernate in cool winter areas. They range in size from 2-in.-long (5-cm) lizards to 30-ft-long (9-m) snakes.

They typically have low-slung bodies with long tails, supported by four short legs that project outward from the sides of the body; however, all snakes are limbless. Although reptiles are fundamentally a terrestrial group, some are adapted to living in water. All breathe air by means of lungs and have thick, waterproof skins designed for retaining body moisture. Unlike amphibians amphibian, in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (order Urodela, or Caudata), and the caecilians, or limbless amphibians (order ..... Click the link for more information. , they do not possess gills or breathe water at any stage of their development, and nearly all lay their eggs or bear their young on land. The reptilian egg has a porous shell and a system of membranes designed to protect the embryo from desiccation. It also has a large quantity of yolk for nourishment. This type of egg is typical of terrestrial vertebrates, and is very different from the simple, unprotected eggs of fishes and amphibians, which are laid in the water.

Fertilization is internal in reptiles, and males have copulatory organs. Females of most species lay eggs, but in some the egg is incubated and hatched internally. In a very few there is true live birth, with the young nourished by a primitive placenta instead of an egg yolk. Types of Reptiles Living reptiles are classified in four orders. The turtles turtle, a reptile of the order Chelonia, with strong, beaked, toothless jaws and, usually, an armorlike shell. The shell normally consists of bony plates overlaid with horny shields. ..... Click the link for more information. , order Chelonia, have a protective bony shell, usually covered with horny plates. They are mostly aquatic in habits although some (see tortoise tortoise , common name for a terrestrial turtle, especially one of the family Testudinidae. Tortoises inhabit warm regions of all continents except Australia. They have club-shaped feet with reduced toes adapted for walking on land, and nearly all have high-domed shells. ..... Click the link for more information. ) are adapted to land. They are the oldest living reptiles, having existed nearly unchanged since the Triassic period.

Members of the order Crocodilia, which includes alligators alligator, large aquatic reptile of the genus Alligator, in the same order as the crocodile. There are two species—a large type found in the S United States and a small type found in E China. Alligators differ from crocodiles in several ways. ..... Click the link for more information. , caimans, crocodiles crocodile, large, carnivorous reptile of the order Crocodilia, found in tropical and subtropical regions. Crocodiles live in swamps or on river banks and catch their prey in the water. They have flattened bodies and tails, short legs, and powerful jaws. ..... Click the link for more information. , and gavials gavial , large reptile of the crocodile order, found in rivers from Pakistan to Myanmar. Also called gharial, the gavial (Gavialis gangeticus) is distinguished from the crocodiles and alligators by its extremely long, slender, parallel-sided snout. ..... Click the link for more information. , are large, carnivorous reptiles of tropical and subtropical swamps and rivers.

They constitute the only remaining order of the great reptilian subclass Archosauria, or ruling reptiles, which includes the extinct dinosaurs dinosaur [Gr., = terrible lizard], extinct land reptile of the Mesozoic era. The dinosaurs, which were egg-laying animals, ranged in length from 2 1-2 ft (91 cm) to about 127 ft (39 m). ..... Click the link for more information. . The order Squamata includes the lizards lizard, a reptile of the order Squamata, which also includes the snake. Lizards form the suborder Sauria, and there are over 3,000 lizard species distributed throughout the world (except for the polar regions), with the greatest number found in warm climates. ..... Click the link for more information. (suborder Sauria) and snakes snake, common name for an elongated, limbless reptile of the order Squamata, which also includes the xlizards. Most snakes live on the ground, but some are burrowers, arboreal, or aquatic; one group is exclusively marine. In temperate climates they hibernate. ..... Click the link for more information. (suborder Serpentes).

Nearly all members of this large and successful modern order are terrestrial. The order Rhynchocephalia has a single living member, the tuatara tuatara or tuatera , lizardlike reptile, Sphenodon punctatus, last survivor of the reptilian order Rhynchocephalia, which flourished in the early Mesozoic era before the rise of the dinosaurs. ..... Click the link for more information. , a lizardlike reptile of New Zealand. Evolution Reptiles first evolved from amphibians about 250 million years ago in the Carboniferous period and were dominant in the world's fauna during the Mesozoic era, sometimes called the Age of Reptiles. The dinosaurs, the marine Ichthyosaurus and Plesiosaurus Plesiosaurus , genus of extinct predatory marine reptiles that arose in the Triassic period of geologic time and continued into the Jurassic and Cretaceous periods. Plesiosaurs became extinct at the close of the Mesozoic era. ..... Click the link for more information. , and the flying pterosaurs reached the peak of their development and distribution in the later part of this era (late Cretaceous period).

Mammallike reptiles appeared very early in reptilian history and by the Triassic period had given rise to mammals. Bird ancestors arose from precursors of the dinosaurs; the first known birds lived in the Jurassic. The only reptiles that survived into the Cenozoic era belonged to the presently living orders. The approximately 6,000 living reptile species represent a very small fraction of this once vast class. Bibliography See R. Conant, Field Guide to Reptiles and Amphibians (1958); A. Bellairs, The Life of Reptiles (2 vol., 1970); K. P. Schmidt and R. F. Inger, Living Reptiles of the World (1957, repr. 1972); H. M. Smith and E. Brodie, Reptiles of North America (1982); H. M. Smith and H. S. Zim, Reptiles and Amphibians (1987). What does it mean when you dream about a reptile? See Dinosaur, Lizard, Serpent, Snake, or Turtle.

reptile Reptile | Define Reptile at Dictionary.com reptile [rep-til, -tahyl] /ˈrɛp tɪl, -taɪl/ Spell noun 1. any cold-blooded vertebrate of the class Reptilia, comprising the turtles, snakes, lizards, crocodilians, amphisbaenians, tuatara, and various extinct members including the dinosaurs. 2. (loosely) any of various animals that crawl or creep. 3. a groveling, mean, or despicable person. adjective of or resembling a reptile; creeping or crawling. 5.

Late Latin 1350-1400 1350-1400; Middle English reptil < Late Latin rēptile, noun use of neuter of rēptilis creeping, equivalent to Latin rēpt(us) (past participle of rēpere to creep) + -ilis -ile Related forms [rep-tl-oid] /ˈrɛp tlˌɔɪd/ (Show IPA), adjective Dictionary.com Unabridged Examples from the Web for reptile Expand Contemporary Examples A reptile hatching from an egg must not cry out for its mother, or else it will be readily detected by predators and eaten. Sage Advice from Famous Dads Bruce Feiler June 18, 2010 Historical Examples The reptile of this name, carrying a virulent and deadly sting in its tail, is generally borne erect. Fire Island G. Manville Fenn At the first onset the reptile had used every effort to retreat in that direction. British Dictionary definitions for reptile Expand noun 1.

any of the cold-blooded vertebrates constituting the class Reptilia, characterized by lungs, an outer covering of horny scales or plates, and young produced in amniotic eggs. The class today includes the tortoises, turtles, snakes, lizards, and crocodiles; in Mesozoic times it was the dominant group, containing the dinosaurs and related forms 2. a grovelling insignificant person: you miserable little reptile! adjective grovelling or insignificant; mean; contemptible Word Origin C14: from Late Latin reptilis creeping, from Latin rēpere to crawl Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Word Origin and History for reptile Expand n.

late 14c., "creeping or crawling animal," from Old French reptile (early 14c.) and directly from Late Latin reptile, noun use of neuter of reptilis (adj.) "creping, crawling," from rept-, past participle stem of repere "to crawl, creep," from PIE root *rep- "to creep, crawl" (cf. Lithuanian replioju "to creep"). Used of persons of low character from 1749. Precise scientific use began to develop mid-18c., but the word was used as well at first of animals now known as amphibians, including toads, frogs, salamanders; separation of Reptilia (1835 as a distinct class) and Amphibia took place early 19c.; popular use lagged, and reptile still was used late 18c. with sense "An animal that creeps upon many feet" [Johnson, who calls the scorpion a reptile], sometimes excluding serpents. And the terrestrial animals may be divided into quadrupeds or beasts, reptiles, which have many feet, and serpents, which have no feet at all.

[Locke, "Elements of Natural Philosophy," 1689] An inadvertent step may crush the snail That crawls at ev'ning in the public path ; But he that has humanity, forewarn'd, Will tread aside, and let the reptile live. [Cowper, "The Task," 1785] The Old English word for "reptile" was slincend, related to slink . Online Etymology Dictionary, © 2010 Douglas Harper reptile (rěp'tīl') Any of various cold-blooded vertebrates of the class Reptilia, having skin covered with scales or horny plates, breathing air with lungs, and usually having a three-chambered heart. Unlike amphibians, whose eggs are fertilized outside the female body, reptiles reproduce by eggs that are fertilized inside the female. Though once varied, widespread, and numerous, reptilian lineages, including the pterosaurs, ichthyosaurs, plesiosaurs, and dinosaurs, have mostly become extinct (though birds are living descendants of dinosaurs).

The earliest reptiles were the cotylosaurs (or stem reptiles) of the late Mississippian or early Pennsylvanian Period, from which mammals evolved. Modern reptiles include crocodiles, snakes, turtles, and lizards. The American Heritage® Science Dictionary Copyright © 2002. Published by Houghton Mifflin. All rights reserved. Reptiles | Article about Reptiles by The Free Dictionary Reptiles | Article about Reptiles by The Free Dictionary reptile, name for the dry-skinned, usually scaly, cold-blooded vertebrates (see Chordata Chordata , phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals. ..... Click the link for more information. ) of the order Reptilia. Reptiles are found in a variety of habitats throughout the warm and temperate regions (except on some islands), with the greatest variety in the tropics.

Reptiles differ from other terrestrial vertebrates (birds and mammals) in that they are cold-blooded, that is, they lack an effective system for regulating their body temperature, which tends to approach that of the environment. For this reason reptiles are not found in the coldest regions of the world, and they hibernate in cool winter areas. They range in size from 2-in.-long (5-cm) lizards to 30-ft-long (9-m) snakes. They typically have low-slung bodies with long tails, supported by four short legs that project outward from the sides of the body; however, all snakes are limbless. Although reptiles are fundamentally a terrestrial group, some are adapted to living in water. All breathe air by means of lungs and have thick, waterproof skins designed for retaining body moisture. Unlike amphibians amphibian, in zoology, cold-blooded vertebrate animal of the class Amphibia. There are three living orders of amphibians: the frogs and toads (order Anura, or Salientia), the salamanders and newts (order Urodela, or Caudata), and the caecilians, or limbless amphibians (order ..... Click the link for more information.

, they do not possess gills or breathe water at any stage of their development, and nearly all lay their eggs or bear their young on land. The reptilian egg has a porous shell and a system of membranes designed to protect the embryo from desiccation. It also has a large quantity of yolk for nourishment. This type of egg is typical of terrestrial vertebrates, and is very different from the simple, unprotected eggs of fishes and amphibians, which are laid in the water. Fertilization is internal in reptiles, and males have copulatory organs. Females of most species lay eggs, but in some the egg is incubated and hatched internally. In a very few there is true live birth, with the young nourished by a primitive placenta instead of an egg yolk. Types of Reptiles Living reptiles are classified in four orders. The turtles turtle, a reptile of the order Chelonia, with strong, beaked, toothless jaws and, usually, an armorlike shell. The shell normally consists of bony plates overlaid with horny shields. ..... Click the link for more information. , order Chelonia, have a protective bony shell, usually covered with horny plates.

They are mostly aquatic in habits although some (see tortoise tortoise , common name for a terrestrial turtle, especially one of the family Testudinidae. Tortoises inhabit warm regions of all continents except Australia. They have club-shaped feet with reduced toes adapted for walking on land, and nearly all have high-domed shells. ..... Click the link for more information. ) are adapted to land. They are the oldest living reptiles, having existed nearly unchanged since the Triassic period. Members of the order Crocodilia, which includes alligators alligator, large aquatic reptile of the genus Alligator, in the same order as the crocodile. There are two species—a large type found in the S United States and a small type found in E China. Alligators differ from crocodiles in several ways. ..... Click the link for more information. , caimans, crocodiles crocodile, large, carnivorous reptile of the order Crocodilia, found in tropical and subtropical regions. Crocodiles live in swamps or on river banks and catch their prey in the water. They have flattened bodies and tails, short legs, and powerful jaws. ..... Click the link for more information.

, and gavials gavial , large reptile of the crocodile order, found in rivers from Pakistan to Myanmar. Also called gharial, the gavial (Gavialis gangeticus) is distinguished from the crocodiles and alligators by its extremely long, slender, parallel-sided snout. ..... Click the link for more information. , are large, carnivorous reptiles of tropical and subtropical swamps and rivers. They constitute the only remaining order of the great reptilian subclass Archosauria, or ruling reptiles, which includes the extinct dinosaurs dinosaur [Gr., = terrible lizard], extinct land reptile of the Mesozoic era. The dinosaurs, which were egg-laying animals, ranged in length from 2 1-2 ft (91 cm) to about 127 ft (39 m). ..... Click the link for more information. . The order Squamata includes the lizards lizard, a reptile of the order Squamata, which also includes the snake. Lizards form the suborder Sauria, and there are over 3,000 lizard species distributed throughout the world (except for the polar regions), with the greatest number found in warm climates. .....

Click the link for more information. (suborder Sauria) and snakes snake, common name for an elongated, limbless reptile of the order Squamata, which also includes the xlizards. Most snakes live on the ground, but some are burrowers, arboreal, or aquatic; one group is exclusively marine. In temperate climates they hibernate. ..... Click the link for more information. (suborder Serpentes). Nearly all members of this large and successful modern order are terrestrial. The order Rhynchocephalia has a single living member, the tuatara tuatara or tuatera , lizardlike reptile, Sphenodon punctatus, last survivor of the reptilian order Rhynchocephalia, which flourished in the early Mesozoic era before the rise of the dinosaurs. ..... Click the link for more information. , a lizardlike reptile of New Zealand. Evolution Reptiles first evolved from amphibians about 250 million years ago in the Carboniferous period and were dominant in the world's fauna during the Mesozoic era, sometimes called the Age of Reptiles.

The dinosaurs, the marine Ichthyosaurus and Plesiosaurus Plesiosaurus , genus of extinct predatory marine reptiles that arose in the Triassic period of geologic time and continued into the Jurassic and Cretaceous periods. Plesiosaurs became extinct at the close of the Mesozoic era. ..... Click the link for more information. , and the flying pterosaurs reached the peak of their development and distribution in the later part of this era (late Cretaceous period). Mammallike reptiles appeared very early in reptilian history and by the Triassic period had given rise to mammals. Bird ancestors arose from precursors of the dinosaurs; the first known birds lived in the Jurassic. The only reptiles that survived into the Cenozoic era belonged to the presently living orders. The approximately 6,000 living reptile species represent a very small fraction of this once vast class. Bibliography See R. Conant, Field Guide to Reptiles and Amphibians (1958); A. Bellairs, The Life of Reptiles (2 vol., 1970); K. P. Schmidt and R. F.

Inger, Living Reptiles of the World (1957, repr. 1972); H. M. Smith and E. Brodie, Reptiles of North America (1982); H. M. Smith and H. S. Zim, Reptiles and Amphibians (1987). What does it mean when you dream about a reptile? See Dinosaur, Lizard, Serpent, Snake, or Turtle. reptile Ichthyosaurs - The "Fish Lizards" Ichthyosaurs - The "Fish Lizards" The Dolphin-Like Marine Reptiles of the Early Mesozoic Era A classic early depiction of ichthyosaurs on the go (Heinrich Harder). By Bob Strauss Updated June 08, 2016. There's an important concept in biology known as "convergent evolution": animals that occupy similar evolutionary niches tend to adopt roughly similar forms.

Ichthyosaurs (pronounced ICK-thee-oh-sores) are an excellent example: starting about 200 million years ago, these marine reptiles evolved body plans (and behavioral patterns) strikingly similar to those of the modern dolphins and bluefin tuna that populate the world's oceans today. (See a gallery of ichthyosaur pictures .) Ichthyosaurs (Greek for "fish lizards") were similar to dolphins in another, perhaps even more telling way. It's believed that these undersea predators evolved from a population of archosaurs (the family of terrestrial reptiles that preceded the dinosaurs) that ventured back into the water during the early Triassic period. Analogously, dolphins and whales can trace their descent to ancient, four-legged prehistoric mammals (like Pakicetus ) that gradually evolved in an aquatic direction. continue reading below our video 4 Tips for Improving Test Performance The First Ichthyosaurs Anatomically speaking, it's relatively easy to distinguish the early ichthyosaurs of the Mesozoic Era from more advanced genera.

The ichthyosaurs of the middle to late Triassic period, such as Grippia , Utatsusaurus and Cymbospondylus , tended to lack dorsal (back) fins and the streamlined, hydrodynamic body shapes of later members of the breed. (Some paleontologists doubt that these reptiles were true ichthyosaurs at all, and hedge their bets by calling them proto-ichthyosaurs or "ichthyopterygians.") Most early ichthyosaurs were fairly small, but there were exceptions: the gigantic Shonisaurus , the state fossil of Nevada, may have attained lengths of 60 or 70 feet! Although the exact evolutionary relationships are far from certain, there's some evidence that the appropriately named Mixosaurus may have been a transitional form between early and later ichthyosaurs. As reflected by its name (Greek for "mixed lizard"), this marine reptile combined some primitive features of early ichthyosaurs--a downward-pointing, relatively inflexible tail and short flippers--with the sleeker shape and (presumably) faster swimming style of their later descendants.

Also, unlike the case for most ichthyosaurs, fossils of Mixosaurus have been discovered all over the world, a clue that this marine reptile must have been especially well-adapted to its environment. Trends in Ichthyosaur Evolution The early to middle Jurassic period (about 200 to 175 million years ago) was the golden age of ichthyosaurs, witnessing important genera like Ichthyosaurus , which is represented today by hundreds of fossils, as well as the closely related Stenopterygius . Besides their streamlined shapes, these marine reptiles were distinguished by their solid ear bones (which conveyed subtle vibrations in the water created by the movement of prey) and large eyes (the eyeballs of one genus, Ophthalmosaurus , were four inches wide!) By the end of the Jurassic period, most ichthyosaurs had gone extinct--though one genus, Platypterygius , survived into the early Cretaceous period, possibly because it had evolved the ability to feed omnivorously (one fossil specimen of this ichthyosaur harbors the remains of birds and baby turtles). Why did the ichthyosaurs vanish from the world's oceans?

The answer may lie in the evolution of speedier prehistoric fish (which were able to avoid being eaten), as well as better-adapted marine reptiles like plesiosaurs and mosasaurs . However, a recent discovery may throw a monkey wrench into accepted theories about ichthyosaur evolution. Malawania plied the oceans of central Asia during the early Cretaceous period, and it retained the primitive, dolphin-like body plan of genera that lived tens of millions of years before. Clearly, if Malawania could prosper with such a basal anatomy, not all ichthyosaurs were "out-competed" by other marine reptiles, and we'll have to adduce other reasons for their disappearance. Ichthyosaur Lifestyles and Behavior Despite the resemblance of some species to dolphins or bluefin tuna, it's important to remember that ichthyosaurs were reptiles, and not mammals or fish. All of these animals did, however, share a similar set of adaptations to their marine environment. Like dolphins, most ichthyosaurs are believed to have given birth to live young, rather than laying eggs like contemporary land-bound reptiles. (How do we know this?

The specimens of some ichthyosaurs, like Temnodontosaurus , were fossilized in the act of giving birth.) Finally, for all their fish-like characteristics, ichthyosaurs possessed lungs, not gills--and therefore had to surface on a regular basis for gulps of air. It's easy to imagine schools of, say, Excalibosaurus frolicking above the Jurassic waves, perhaps sparring with one another with their swordfish-like snouts (an adaptation evolved by some ichthyosaurs to spear any unfortunate fish in their path). A Complete List of Ichthyosaurs Acamptonectes This "rigid swimmer" was closely related to Ophthalmosaurus. Brachypterygius A big-eyed cousin of Ophthalmosaurus. Californosaurus Guess what state this ichthyosaur was discovered in? Cymbospondylus A very large--and very ancient--ichthyosaur. Dearcmhara This ichthyosaur lived in middle Jurassic Scotland. Eurhinosaurus This ancient ichthyosaur looked like a modern sawfish. Excalibosaurus This ichthyosaur was named after King Arthur’s sword. Grippia The best specimen of this ichthyosaur was destroyed in World War II.

Ichthyosaurus A remarkably fish-like lizard of the Jurassic period. Malawania A dolphin-like ichthyosaur of the early Cretaceous period. Mixosaurus This "mixed lizard" may be the the missing link of ichthyosaurs. Nannopterygius The most common ichthyosaur in the fossil record. Omphalosaurus This "button lizard" may or may not have been a genuine ichthyosaur. Ophthalmosaurus An ocean-dwelling ichthyosaur distinguished by its large eyes. Platypterygius One of the rare ichthyosaurs to survive into the Cretaceous period. Shastasaurus This ichthyosaur fed on soft-bodied cephalopods. Shonisaurus The largest ichthyosaur yet to be discovered. Stenopterygius A close relative of Ichthyosaurus. Temnodontosaurus A dolphin-shaped ichthyosaur that gave birth to live young. Utatsusaurus The most ancient ichthyosaur yet discovered. The History of Life - Reptiles Reptiles: Early Consumers on Land Evolutionary Novelty: New morphological innovations that define newly established groups: The amniotic egg: a space capsule for the reptilian embryo.

The major evolutionary step to a fully terrestrial existence was accomplished primarily due to innovation in reproduction. As one of their diagnostic features, reptiles have an amniote egg, a reproductive character that eventually allowed them to dominate many available land habits. Diagnostic features that developed in the gradual evolution of amphibians to reptiles: Fairly com­mon intermediate forms that combined a blend of typical amphibian and reptilian characters (see figure below). In general, early reptiles stabilized a particular style of back­bone construction. The lack of an otic notch in reptiles, the ear being situated at the rear of the skull. Bones of the back part of the reptilian skull are reduced in number and size, a continuation of the trend present from rhipidistian fish to amphibians. A mounted skeleton of the Permian amphibian Seymouriafrom Central Texas (see image). This small animal, approximately 60 cm (2 ft) long, shows a unique blend of amphibian and reptilian characters but is much too young to have been the direct ancestor of reptiles. Notice that an otic notch is still present in the back of the skull.

Other anatomical features resemble those of reptiles.(Courtesy of National of Natural History.) How to tell early reptiles from others The most important feature for distinguishing one type of early reptile from another is the structure of the bones in the temple region of the skull, behind the eye, called temporal openings, whichprovide data that is used in subdividing all major reptile groups. The reptiles of this group are referred to as stem reptiles or anapsidsbecause they are the ones from which the other, more advanced reptiles are thought to have evolved. The only living anapsids are the turtles and tortoises (see figure below) The synapsids: or mammal-like reptiles have a single temporal opening low on the side of the skull, beneath the postorbital and squamosal bones. They are extinct but very important because mammals evolved from this group of reptiles. The diapsids: or ruling reptiles have two openings, one above the other, separated by a bony connection between the postorbital and squamosal bones. They include the dinosaurs of the Mesozoic Era, as well as most living reptiles-the crocodiles, alligators, snakes, and lizards.

The euryapsids: have a single opening high on the skull, above the postorbital and squamosal bones, a condition derived from their diapsid ancestor. Include the ichthyosaurs and plesiosaurs. Most euryapsids had an aquatic or semiaquatic way of life. Thecodonts: important diapsid group which gave rise to the groups known as dinosaurs before the close of the Triassic. The thecodonts first appeared during the Early Triassic and became extinct at the close of the system. Some the­codonts ran on all four legs (quadrupedal), others exhibited a new bipedal, or two-legged stance. By the end of the Triassic, thecodonts had given rise to both groups of dinosaurs, the Saurischia and Ornithischia The Saurischia (lizard-hipped): the termcomes from sauria, meaning reptile, and ischia, referring to the ischium bone of the pelvis. These dinosaurs had a pelvis built like that of many other reptiles, hence the name lizard-hipped dinosaurs.From them evolved the other major group of dinosaurs.

The Ornithischia (bird-hipped):which appeared at the end of the Triassic. This group had a birdlike pelvis. REPTILES Different subclasses are distinguished by skull structure Anapsids: no holes on side of skull (turtles, extinct primitive [stem] reptiles) Synapsids: 1 hole on lower side of skull (extinct mammal-like [pelycosaur & therapsid] reptiles). Synapsids ('fused arch'), also known as theropsids ('beast face'), are a class of animals that includes mammals and everything closer to mammals than to other living amniotes.The non-mammalian members were traditionally described as mammal-like reptiles, and are sometimes referred to as "proto-mammals" or "stem-mammals". Euryapsids: 1 hole on upper side of skull (most extinct marine reptiles. Examples of euryapsids are: icthyosaur, plesiosaur, nothosaur, placodont. This group of reptiles is included in the informal class Euryapsida which is considered to be an unnatural, polyphyletic group, as the various members are not closely related.

This group of reptiles is distinguished by a single temporal fenestra, an opening behind the orbit, under which the post-orbital and squamosal bones articulate.

Diapsids: 2 HOLES on side of skull (MOST LIVING REPTILES [lizard, snake, crocodile, tuatara]; extinct DINOSAURS; extinct FLYING [pterosaur] REPTILES, & MOSASAURS [extinct marine reptiles]) DIAPSIDS: 2 HOLES on side of skull (MOST LIVING REPTILES [lizard, snake, crocodile, tuatara]; extinct DINOSAURS; extinct FLYING [pterosaur] REPTILES, & MOSASAURS [extinct marine reptiles]) Many new reptile types appeared in the Triassic TURTLES (Mesozoic turtles had teeth); TUATARAS: lizards of New Zealand CROCODILES (Cretaceous forms got to be as long as 15 m) LIZARDS & SNAKES (snakes evolved from lizards by the Cretaceous) MARINE & FLYING REPTILES & DINOSAURS (see below) THECODONTS (teeth set in sockets) - a MOSTLY BIPEDAL GROUP that GAVE RISE to CROCODILES, LIZARDS, SNAK

ES, FLYING REPTILES & DINOSAURS The Triassic land fauna was dominated by therapsids & thecodonts MARINE REPTILES Several groups with marine adaptations, including paddle-shaped limbs, streamlined bodies, & reproductive adaptations for birth of young at sea.

Euryapsids:PLACODONTS; NOTHOSAURS; PLESIOSAURS (long necks; short, tailless bodies; flippers); ICTHYOSAURS (MOST FISH-LIKE MARINE REPTILE [convergent with dolphins]) Anapsids:SEA TURTLES Diapsids: MARINE CROCODILES OCCURRED MOSTLY DURING JURASSIC; MOSASAURS (SHORT NECKS; LONG BODIES & TAILS) Diapsid Skull: The name Diapsida means "two arches", and diapsids are traditionally classified based on their two ancestral skull openings (temporal fenestrae) posteriorly above and below the eye. Synapsid Skull: Synapsids evolved a temporal fenestra behind each eye orbit on the lateral surface of the skull. It may have evolved to provide new attachment sites for jaw muscles. Anapsid Skull: An anapsid is an amniote whose skull does not have openings near the temples Euryapsid Skull: distinguished by a single temporal fenestra , an opening behind the orbit, under which the post-orbital and squamosal bones articulate.

j: jugal Images source: Therapsids: "mammal-like reptiles" cynodonts : ancestor of Mammalia. Thecodont ("socket-toothed" reptile), now considered an obsolete term, was formerly used to describe a diverse range of early archosaurs that first appeared in the Latest Permian and flourished until the end of the Triassic period. The group includes the ancestors of dinosaurs (including birds), and ancestors of pterosaurs, and crocodilians, as well as a number of extinct forms that did not give rise to any descendants. - Theropods - Theropods are a group of bipedal saurischian dinosaurs. Although they were primarily carnivorous, a number of theropod families evolved herbivory during the Cretaceous System. Theropods first appear during the Carnian stage of the Upper Triassic about 220 million years ago (MYA) and were the sole large terrestrial carnivores from the Lower Jurassic until the close of the Cretaceous, about 65 MYA. Today, they are represented by the 9,300 living species of birds, which evolved in the Upper Jurassic from small specialized coelurosaurian dinosaurs.

- Tetrapoda: "four feet" thecodonts Archosauria (the "ruling reptiles": is a major group of diapsids, differentiated from the other diapsids by the presence of single openings in each side of the skull, in front of the eyes (antorbital fenestrae), among other characteristics. The ancestral archosaurs probably originated some 250 million years or so ago, in the upper Permian period. Their descendants (such as the dinosaurs) dominated the realm of the terrestrial vertebrates for a majority of the Mesozoic Era. Today, only the birds and crocodilians exist to provide a glimpse into the past glory of archosaurs.

THE DINOSAURS 1.Evolved in the Triassic & expanded & diversified in the Jurassic & Cretaceous 2.Traditionally divided into two orders based on hip structure: Saurischia (lizard-hipped) & Ornithischia (bird-hipped) 3.Early dinosaurs were mostly Saurichians, which are divided into 2 suborders: (a) Bipedal carnivorous theropods, and (b) giant, 4-footed herbivorous sauropods 4.The Ornithischians are divided into 5 suborders:Stegosaurs, Ankylosaurs, Ceratopsians, Ornithopods, and Pachycephalosauria All were herbivorous with the front teeth replaced by a beak & cheek teeth adapted for crushing coarse vegetation Ornithopods, ankylosaours & ceratopsians were low browsers and were the dominant herbivores during the cretaceous Note: Robert Bakker has suggested that replacement of high browsing sauropods by low browsing ornithischians aided fast growing angiosperms in replacing slow growing gymnosperms as the dominant land plant Arguments in favor of warm-bloodedness (

Endothermy) Predator to prey ratios; erect stance; richly vascularized bones; growth rates; social behavior & migration of herds; hair on flying reptiles; complete dominance over mammals Arguments in favor of cold-bloodedness (Ectothermy) Dinosaurs were reptiles & modern reptiles are cold-blooded; erect stance & vascularized bones were responses to large size; large size itself Still an open question NOTE: it is no longer accepted that dinosaurs were slow & ponderous; dinosaur behavior probably like bird & mammal behavior.

Theropods were quick & agile; large sauropods & ornithischians assembled in social herds; smaller sauropods & ornithischians behaved in a birdlike way. SUMMARY OF DINOSAUR TAXONOMY Iguanodon Parasaurolophus Some ornithopods, such as Apatosaurus, had a bill-like mouth and are called duck-billed dinosaurs. Size from a few meters Long up to 13 m and 3.6 metric tons. Especially diverse and common during the Cretaceous. Primarily bipedal herbivores, but could also walk on all fours. Pachycephalosauria Stegoceras Stegoceras only 2 m Long and 55 kg, but larger species known. Thick bones of skull cap might have aided in butting contests for dominance and mates. Bipedal herbivores of Cretaceous. Ankylosauria Ankylosaurus Ankylosaurus more than 7 m Long and about 2.5 metric tons. Heavily armored with bony plates on top of head, back, and sides. Quadrupedal herbivore.

Stegosauria Stegosaurus A variety of stegosaurs are known, but Stegosaurus, with bony plates on its back and a spiked tail is best known. Plates probably were for absorbing and dissipating heat. Quadrupedal herbi­vores that were most common during the Jurassic. Stegosaurus 9 m Long, 1.8 metric tons. Ceratopsia Triceratops Numerous genera known. Some early ones bipedal, but Later Large animals were Quadrupedal herbivores. Much variation in size; Triceratops to 7.6 m Long and 5.4 metric tons, with Large bony frill over top of neck, three horns on skull, and beaklike mouth. Especially common during the Cretaceous. SAURISCHIAN DINOSAURS The saurischians include two dis­tinct groups known as theropods and sauropods(see table above). Theropods(beast-footed): Typical genus Tyrannosaurus;bipedal carnivores.

Upper Triassic to end of Cretaceous.Size from 0.6 to 15 m long, 2 or 3 kg to 7.3 metric tons. Some smaller genera may have hunted in packs. All theropods were carnivorous bipeds that var­ied from tiny Compsognathus to giants such as Tyrannosaurus and similar but even larger species. Other genera include Allosaurus, Compsognathus, Deinonychus, Velociraptor, and Coelophysis. In 1996, Chinese scientists discovered several theropods with feathers. No one doubts that these dinosaurs had feathers, and molecular evidence indicates they were composed of the same material as bird feathers. Sauropods (reptile-footed): Typical genus Brachiosaurus; Giant Quadrupedal herbivores. Upper Triassic to Cretaceous, but most common during Jurassic. Size up to 27 m long, 75 metric tons. Track ways indicate sauropods lived in herds.

Preceded in fossil record by the smaller prosauropods includes the truly giant, quadrupedal herbivorous dinosaurs such as Apatosaurus, Diplodocus, Apatosaurus,Camarasaurus, and Titanosaurus; the largest land animals ever. Brachiosaurus, a gi­ant even by sauropod standards, may have weighed 75 met­ric tons, and partial remains from several areas indicate that even larger sauropods may have existed. Track ways show that sauropods moved in herds. Sauropods were preceded in the fossil record by the smaller Upper Triassic to Lower Jurassic prosauropods, which were undoubtedly related to sauropods but probably not their ancestors. Sauropods were most common during the Jurassic; only a few genera existed during the Cretaceous. ORNITHISCHIAN DINOSAURS All were herbivorous with the front teeth replaced by a beak & cheek teeth adapted for crushing coarse vegetation Ornithopods, ankylosaours and ceratopsians were low browsers and were the dominant herbivores during the cretaceous.

Note: Robert Bakker has suggested that replacement of high browsing sauropods by low browsing ornithischians aided fast growing angiosperms in replacing slow growing gymnosperms as the dominant land plant. Five Classes of Ornithischians are recognized: Ornithopoda, Pachycephalosauria, Anky­losauria, Stegosauria, and Ceratopsia (see table above). Ornithopoda(bird-footed): Typical genus Maiasaura ("good mother dinosaur"). Some ornithopods, such as Apatosaurus, had a bill-like mouth and are called duck-billed dinosaurs. Size from a few meters long up to 13 m and 3.6 metric tons. Especially diverse and common during the Cretaceous. Primarily bipedal herbivores, but could also walk on all fours. Consist of several subgroups, including the familiar duck-billed dinosaurs or hadrosaurs. Hadrosaurs (duck-billed dinosaurs) were especially numerous during the Cretaceous, and several species had head crests that may have been used to amplify bellowing, for sexual display, or for species recognition.

All ornithopods were herbivorous and pri­marily bipedal, but they had well-developed front limbs that allowed them to walk in a quadrupedal fashion, too. The Upper Cretaceous ornithopods Miasaura ("good mother dinosaur") nested in colonies and used the same nesting area repeatedly where 2 m diameter nests were placed 7 m apart or about the length of an adult. Some nests contain juveniles up to 1 m long, which is much larger than when they hatched, so they probably stayed in the nest area where adults protected them and perhaps fed them. The fact that these animals lived in vast herds is demonstrated by the fossils of an estimated 10,000 individuals in a single bone bed in Montana. Apparently they were overcome by toxic gases from a volcano and later buried in flood deposits. Other genera included in this class are Hypsilophodon (' high-ridge tooth'), Iguanodon, and Parasaurolophus View some specimens of Maiasaura Pachycephalosauria: Typical genus: Stegoceras; only 2 m Long and 55 kg, but larger species known.

Thick bones of skull cap might have aided in butting contests for dominance and mates. Bipedal herbivores of Cretaceous. The most distinctive feature of the pachycephalosaurs is their thick-boned, dome-shaped skull. The traditional view of these as animals that butted heads for dominance or mates has been challenged. Now some paleon­tologists note that the thick skull bones are found only in ju­veniles but not in adults. In any case, pachycephalosaurs were bipedal herbivores that varied from 1 to 4.5 m long. Their fossils are known only from Late Cretaceous-aged rocks. Ceratopsia (horned dinosaurs):Typical genus Triceratops. Numerous genera known. Some early ones bipedal, but Later Large animals were Quadrupedal herbivores. Much variation in size; Triceratops to 7.6 m Long and 5.4 metric tons, with Large bony frill over top of neck, three horns on skull, and beaklike mouth.

Especially common during the Cretaceous.The fossil record of ceratopsians (horned dinosaurs) shows that small Lower Cretaceous animals were the ancestors of large Upper Cretaceous genera such as Triceratops. Triceratops and related genera with huge heads, a large bony frill over the neck, and a horn or horns on the skull were very common in North America. Fossil track ways show that these large, quadrupedal herbivores moved in herds. Furthermore, bone beds with fossils from a single species indicate that large numbers of ceratopsians perished quickly, probably during river crossings. Stegosauria: Typical genus Stegosaurus. A variety of stegosaurs are known, but Stegosaurus, with bony plates on its back and a spiked tail is best known. Plates probably were for absorbing and dissipating heat. Quadrupedal herbi­vores were most common during the Jurassic. Stegosaurus 9 m long, 1.8 metric tons.The most distinctive features of Stegosaurus include being a medium-sized, herbivorous quadruped from the Jurassic System, are a spiked tail, almost certainly used for defense, and plates on its back.

The exact arrangement of these plates is uncertain, although they are usually depicted in two rows with the plates on one side offset from those on the other. In any case, most paleontol­ogists think the plates functioned to absorb and dissipate heat. Ankylosauria: Typical genus Ankylosaurus, more than 7 m Long and about 2.5 metric tons. Heavily armored with bony plates on top of head, back and sides. Quadrupedal herbivore. Were quadrupedal herbivores and more heavily armored than any other dinosaur. Bony armor protected the animal's back, flanks, and top of the head. The tail of some species such as Ankylosaurus ended in a bony club that undoubtedly could de­liver a crippling blow to an attacking predator. Flying Reptiles First flying reptiles - gliders Pterosaurs - active flyers with maneuvering ability, wings were skin stretched between elongated 4th finger, sides of the body & rear limbs.

Pterosaurs were warm-blooded - fine hair covers well preserved pterosaurs Paleozoic insects were the first animals to achieve flight, but the first among vertebrates were pterosaurs, or flying reptiles, which were common in the skies from the Upper Triassic until their extinction at the end of the Cretaceous. Adaptations for flight include a wing membrane supported by an elongated fourth finger, light, hollow bones; and development of those parts of the brain that con­trolled muscular coordination and sight. Because at least one pterosaur species had a coat of hair or hair like feathers, possi­bly it, and it is likely that all pterosaurs, were endotherms. Pterosaurs : Are generally depicted in movies as large, aggressive creatures, but some were no bigger than to day's sparrows, robins, and crows. However, a few species had wingspans of several meters, and the wingspan of one Cre­taceous pterosaur was at least 12 m.

Nevertheless, even the very largest species probably weighed no more than a few tens of kilograms.Experiments and studies of fossils indicate that the wing bones of large pterosaurs such as Pteranodon were too weak for sustained flapping. These comparatively large animals probably took advantage of rising air currents to stay airborne, mostly by soaring but occasionally flapping their wings for maneuvering. In contrast, smaller pterosaurs probably stayed aloft by vigorously flapping their wings just as present-day small birds do. PTERODACTYLOIDS - advanced pterosaurs with no tails & some had enormous wingspans: - Pteranodon = 7 m; Quetzalcoatlusnorthropi = 15.5 m Mesozoic Marine Reptiles Several types of Mesozoic reptiles adapted to a marine en­vironment, including turtles and some crocodiles, and the Triassic mollusk-crushing placodonts. Best know exaples of marine reptilesareichthyosaurs, plesiosaurs and mosasaurs. Ichthyosaurs :Used their powerful tail for propulsion and maneuvered with their flipper like forelimbs.

They had nu­merous sharp teeth, and preserved stomach contents reveal a diet of fish, cephalopods, and other marine organisms. It is doubtful that ichthyosaurs could come onto land, so females must have retained eggs within their bodies and given birth to live young. A few fossils with small ichthyosaurs in the ap­propriate part of the body cavity support this interpretation. Plesiosaurs :Belonged to one of two subgroups: short-necked and long-necked. Most were modest-sized animals 3.6 to 6 m long, but one species found in Antarctica measures 15 m. Short-necked ple­siosaurs might have been bottom feeders, but their long­necked cousins may have used their necks in a snakelike fashion, and their numerous sharp teeth, to capture fish. These animals probably came ashore to lay their eggs. Mosasaurs :They were Upper Cretaceous marine lizards related to the present-day Komodo dragon or monitor lizard. Some species measured no more than 2.5 m long, but a few such as Tylosaurus were large, measuring up to 9 m.

Mosasaur limbs resemble paddles and were used mostly for maneuvering, whereas the long tail provided propulsion. Crocodiles, Turtles, Lizards, and Snakes Crocodiles: They develop since Jurassic time, crocodiles had become the most common freshwater predators. All crocodiles are amphibious, spend­ing much of their time in water, but they are well equipped for walking on land. Overall, crocodile evolution has been conservative, involving changes mostly in size from a meter or so in Jurassic forms to 15 m in some Cretaceous species. Turtles: Have been evolutionarily conservative since their appearance during the Triassic. The most remarkable feature of turtles is their heavy, bony armor; turtles are more thoroughly armored than any other vertebrate animal, liv­ing or fossil. Turtle ancestry is uncertain. One Permian ani­mal had eight broadly expanded ribs, which may represent the first stages in the development of turtle armor. Lizards and snakes:Are closely related, and lizards were in fact ancestral to snakes. The limbless condition in snakes (some lizards are limbless, too) and skull mod­ifications that allow snakes to open their mouths very wide are the main difference between these two groups.

Lizards are known from Upper Permian strata, but they were not abundant until the Upper Cretaceous. Snakes first appear in the Cretaceous, but the families to which most living snakes belong differentiated since the Early Miocene. One Lower Cretaceous genus from Israel shows characteristics intermediate between snakes and their lizard ancestors.

Question: 'Fish lizard' is the literal meaning of which extinct reptile's name?
Answer: Ichthyosaur